Chemical-mechanical polishing apparatus with megasonic energy slurry supply system

ABSTRACT

An apparatus for chemical-mechanical polishing is disclosed. The apparatus includes the following elements. A pump is used for forcing slurry to be flown inward to receive the slurry from a supply reservoir. A first pipe having a first end, is coupled to an outlet of the forcing means through which the forced slurry flows therein. A megasonic generator coupled in approximately midway of the first pipe and surrounded the first pipe, is used for generating megasonic wave. A second pipe, coupled to a second end of the first pipe, is used for conducting the slurry and then exhausting the slurry through an outlet of the second pipe. A polishing pad, onto that the slurry from the second pipe is dropped, is fixed on a polishing table. The polishing table underlying the polishing pad is used for supporting the polishing pad. A wafer holder, located above the polishing pad, is used for fixing the wafer to the wafer holder while in rotational movement with respect to the polishing pad.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to apparatus for manufacturing semiconductor, more particularly to apparatus for chemical-mechanical polishing process.

[0003] 2. Description of the Prior Art

[0004] Chemical-mechanical polishing (CMP) is one of the common planarizing techniques. The method is used to achieve a planar surface over the entire chip and wafer, referred to as “global planarity”. It consists of a rotating holder that holds the wafer, an appropriate slurry, and a polishing pad that is applied to the wafer at a specified pressure. CMP is not limited to dielectrics. It is used to planarize deep and shallow trenches filled with polysilicon or oxide, and various metal films.

[0005] Polishing results from a combination of chemical and mechanical effects. A suggested mechanism for CMP involves the formation of a chemically altered layer at the surface of the material being polished. This layer is mechanically removed from the surface, beginning the process again. For example, in SiO2 polishing, the altered layer may be a hydrated oxide that can be mechanically removed or, for metal polishing, a metal oxide may be formed and removed.

[0006] The slurry composition and pad pressure determine the polishing rate. Oxide films, for example, polish twice as fast in a slurry with pH=11 than with pH=7. The hardness of the polishing particles should be about the same as the hardness of the film being polished to avoid damaging the film. The particle size should be uniform, commonly less than 0.1 μm in the diameter, and the solution free of metallic contaminants. Slurry typically consists of an abrasive component and a component that chemically interacts with the surface. A typical oxide polishing slurry may consist of a colloidal suspension of oxide particles, with and average size of 0.03 μm, in an alkali solution (pH≧10). A polishing rate of about 0.12 μm/min can be achieved with this solution.

[0007] A variety of polishing pads/cloths is available. They are typically grouped by their mechanical properties. Hard pads produce better planarity, while soft pads achieve better uniformity and less surface damage. The choice of pads is application dependent. For example, while soft pads are used for flat silicon substrates to avoid scratches, these pads are often not suitable for surfaces containing patterns.

[0008] Several methods to detect the polish end-point are being investigated. Some of them rely on the change in frictional forces between pad and polished surface. The most widely used method is, however, to measure the thickness of the polished film at several intervals between polishing and determine the time needed to achieve the required polished thickness.

[0009] During the polishing process, some polishing particles in the slurry, such as SiO₂, are easily aggregated together and then become a gel or a larger grain that has the size more than 0.5 μm. Unfortunately, the gel or larger grain can usually damage the polished surface of wafer. The aggregation is due to the static and the gelling effects.

[0010] For the foregoing reason, there is a need to develop an apparatus, that can avoid the aggregation of the polishing particles in the slurry during polishing process.

SUMMARY OF THE INVENTION

[0011] In accordance with the present invention, a mechanism is provided for performing chemical-mechanical polishing, that substantially prevents the damages on polished surface of wafer during CMP. In one embodiment, the mechanism includes: a pump for forcing slurry to be flown inward to receive the slurry from a supply reservoir; a first pipe having a first end, coupled to an outlet of the forcing means through which the forced slurry flows therein; a megasonic generator, coupled in approximately midway of the first pipe and surrounded the first pipe; a second pipe coupled to a second end of the first pipe, for further conducting the slurry and then exhausting the slurry through an outlet of the second pipe; a polishing pad onto which the slurry from the second pipe is dropped; a polishing table underlying the polishing pad for supporting the polishing pad; and a wafer holder, located above the polishing pad, for fixing the wafer to the wafer holder while in rotational movement with respect to the polishing pad.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

[0013]FIG. 1 shows the chemical-mechanical polishing mechanism introduced by the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0014] In semiconductor manufacturing, the sonic energy is generally used for cleaning system to loosen particles on wafers. The high frequency sonic waves (about 850 kHz) will be generated in the cleaning process. Similarly, to loosen the particles in polishing slurry, the sonic energy can also be used for chemical-mechanical polishing (CMP) to prevent the situation of polishing particles aggregating together.

[0015] In the present invention, a chemical-mechanical polishing mechanism including a megasonic energy slurry supply system is provided. As shown in FIG. 1, mainly, a megasonic generator 12 is added to the slurry supply system of the conventional CMP mechanism. The slurry includes polishing particles and a solution. Each of the polishing particles has the size about less than 0.1 μm in the diameter, and its selected material is according as the polished object.

[0016] In the mechanism of this invention, a typical peristalsis pump 10 forces slurry to be flown inward to receive the slurry from a supply reservoir. A first pipe 11 having a first end is coupled to an outlet of the peristalsis pump 10 through which the forced slurry flows therein. Therein, the first pipe 11 has an interior passage way configured to conduct the slurry. A megasonic generator 12, which can generate megasonic or sonic wave, is coupled in approximately midway of the first pipe 11 and surrounded the first pipe 11. Therefore, the generated megasonic or sonic wave transmits into and affecting the slurry in the interior passage way of the first pipe 11, thereby grain size of each of the particles in the affected slurry is made small enough or the grains are prevented from being aggregated. Accordingly, the polishing of the chemical-mechanical polishing apparatus can be improved.

[0017] Moreover, a second pipe 13, coupled to a second end of the first pipe 11, for further conducting the slurry and then exhausting the slurry through an outlet of the second pipe 13. Then the slurry from the second pipe 13 is dropped onto a polishing pad 14, therein, the polishing pad 14 is located under the outlet of the second pipe 13. A wafer 17 under polishing and the polishing pad 14 are in rotational contact such that the dropped slurry facilitates the polishing of the chemical-mechanical polishing apparatus. A rotary polishing table 15 underlying the polishing pad 14 is used to support the polishing pad 14. A wafer holder 16, located above the polishing pad 14, is used to fixing the wafer 17 to the rotary wafer holder 16 while in rotational movement with respect to the polishing pad 14.

[0018] Although specific embodiments have been illustrated and described, it will be obvious to those skilled in the art that various modifications may be made without departing from what is intended to be limited solely by the appended claims. 

What is claimed is:
 1. A chemical-mechanical polishing apparatus, comprising: means for forcing slurry to be flown inward to receive the slurry from a supply reservoir; a first pipe having a first end coupled to an outlet of said forcing means through which the forced slurry flows therein, wherein said first pipe has an interior passage way configured to conduct the slurry; means for generating sonic wave, coupled in approximately midway of said first pipe and surrounded said first pipe, therefore said generated sonic wave transmitting into and affecting the slurry in the interior passage way of said first pipe, thereby grain size of the affected slurry is made small enough or the grains of the affected slurry are prevented from being aggregated, thereby improving the polishing of the chemical-mechanical polishing apparatus; a second pipe, coupled to a second end of said first pipe, for further conducting the slurry and then exhausting the slurry through an outlet of said second pipe; a polishing pad onto which the slurry from said second pipe is dropped, wherein said polishing pad is located under the outlet of said second pipe, therefore a wafer under polishing and said polishing pad are in rotational contact such that the dropped slurry facilitates the polishing of the chemical-mechanical polishing apparatus; a polishing table underlying said polishing pad for supporting said polishing pad; and a wafer holder, located above said polishing pad, for fixing the wafer to said wafer holder while in rotational movement with respect to said polishing pad.
 2. The apparatus according to claim 1 , wherein said forcing means includes a pump.
 3. The apparatus according to claim 2 , wherein said pump includes a peristalsis pump.
 4. The apparatus according to claim 1 , wherein said generating means includes a megasonic generator.
 5. The apparatus according to claim 1 , wherein said polishing table includes a rotary polishing table.
 6. The apparatus according to claim 1 , wherein said wafer holder includes a rotary wafer holder.
 7. A slurry supply system for chemical-mechanical polishing (CMP), comprising: means for forcing slurry to be flown inward to receive the slurry from a supply reservoir; a first pipe having a first end coupled to an outlet of said forcing means through which the forced slurry flows therein, wherein said first pipe has an interior passage way configured to conduct the slurry; means for generating sonic wave, coupled in approximately midway of said first pipe and surrounded said first pipe, therefore said generated sonic wave transmitting into and affecting the slurry in the interior passage way of said first pipe, thereby grain size of the affected slurry is made small enough or the grains of the affected slurry are prevented from being aggregated, thereby improving the polishing of the chemical-mechanical polishing apparatus; a second pipe, coupled to a second end of said first pipe, for further conducting the slurry and then exhausting the slurry through an outlet of said second pipe;
 8. The apparatus according to claim 7 , wherein said forcing means includes a pump.
 9. The apparatus according to claim 7 , wherein said pump includes a peristalsis pump.
 10. The apparatus according to claim 7 , wherein said generating and transmitting means includes a megasonic generator. 